Oxalates are anti-nutrients found in green leafy vegetables. Green leafy vegetables provide various health benefits as they contain vitamins, minerals, fibres and phyto-nutrients. Few green leafy vegetables such as spinach, leaves of rhubarb, leaves of beetroot have high levels of oxalates [1].

Spinach is rich source of iron but due to presence of oxalates, the iron absorption is reduced. Oxalates bind with minerals and body can’t make any use of minerals. We do have a bacteria Oxalobacter formigenes in our gastrointestinal system which can convert oxalic acid into formate and carbon-dioxide[2]. The presence or absence of this bacteria is influenced by environmental and genetic factors and thus, some people are more prone to kidney stone formation [3].

Oxalates when bind with calcium, form calcium oxalate crystals which can accumulate in kidneys and can form kidney stone formation. Hence, people with kidney disorders and stone (lithiasis) issues should avoid consumption of raw spinach.

Cooking and boiling reduces the amount of oxalates but the oxalates are leached into cooking water and the nutrients are also lost. Among all the methods of cooking spinach, blanching of spinach and other green leafy vegetables, for 10 to 15 minutes have been found to be effective in removal of oxalates [4]. Blanching means immerse the leaves in hot water, the oxalates will leach into water, therefore discard the water and use the blanched leaves [5].



  1. Natesh H, Abbey L, Asiedu S (2017) An overview of nutritional and antinutritional factors in green leafy vegetables. Horticult Int J 1: 00011.
  2.  Holmes RP, Knight J, Assimos DG (2016) Lowering urinary oxalate excretion to decrease calcium oxalate stone disease. Urolithiasis 44: 27-32.
  3. Das SG, Savage G (2013) Oxalate content of Indian spinach dishes cooked in a wok. Journal of food composition and analysis 30: 125-129.
  4. Yadav SK, Sehgal S (2003) Effect of domestic processing and cooking on selected antinutrient contents of some green leafy vegetables. Plant Foods for Human Nutrition 58: 1-11.
  5. Dagostin JLA (2017) Use of Blanching to Reduce Antinutrients, Pesticides, and Microorganisms. In: Richter Reis F, editor. New Perspectives on Food Blanching. Cham: Springer International Publishing. pp. 61-94.